Fort Independence is a granite star fort that provided harbor defenses for Boston, Massachusetts. Located on Castle Island, Fort Independence is the oldest continuously fortified site of English origin in the United States. The first primitive fortification was placed on the site in 1634 and replaced in 1701 with a more substantial structure known as Castle William. Re-built after it was abandoned by the British during the American Revolution, Castle William was renamed Fort Adams and then Fort Independence. The existing granite fort was constructed between 1833 and 1851. Today it is preserved as a state park and fires occasional ceremonial salutes. Fort Independence was added to the National Register of Historical Places in 1970.